Requirements for Compartmentalization of Penicillin-Binding Proteins during Sporulation in Bacillus subtilis

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Virginia Tech

Penicillin-binding proteins (PBP's) are membrane-associated enzymes involved in the polymerization of peptidoglycan. PBP's are divided into three classes based upon their molecular weights and functional domains. Gene expression is regulated in the two differentiated cells in Bacillus subtilis, the mother cell and the forespore, by coordinated expression of different sigma factors that recognize specific promoters in each compartment. The functional and compartmental specificity of individual penicillin-binding proteins from the different classes of PBP's were examined during sporulation in B. subtilis. Analyses of three class A high molecular weight PBP's indicated that pbpF and pbpG must be expressed in the forespore to carry out their specific role during spore peptidoglycan synthesis. Expressing pbpD in either the forespore or the mother cell could not complement for the loss of pbpF and pbpG, suggesting that there must be additional sequence information in PBP2c and PBP2d that allows them to carry out their specific role during germ cell wall synthesis. Analyses of a low molecular weight PBP, PBP5*, suggested that expressing dacB in either the mother cell or in the forespore could regulate the level of spore peptidoglycan cross-linking to what is typical of wild type spore peptidoglycan.

Bacillus subtilis, endospore, penicillin-binding protein, cortex, PBP, peptidoglycan, sporulation, spore peptidoglycan